It is common practice in coal mines and other mines to fix the ends of roof bolts in holes bored in the mine roof with a thermosetting resin compound. The compound is furnished to the mine encased in a plastic bag or like package that can be inserted into the drilled hole, and usually comprises a resin, such as a polyester, and a curing agent separated from the resin. The package is inserted into the hole; the roof bolt is pushed up against it and rotated to rupture the container and mix the resin and curing agent. The mixing is necessary to achieve a uniform composition of the resin compound. The roof bolt is then held stationary in place while the compound sets or cures. Quick curing resins are generally used which solidify in a few minutes. When the upper end of the roof bolt is bonded to the roof, a perforated plate and nut are applied to its lower end and the nut is tightened to tension the bolt and exert pressure on the roof.
A number of devices have been devised to rotate the roof bolt to mix the resin and then apply tension to the bolt after its end is bonded to the roof. A conventional device is a shear pin of some sort. A drawback of prior art shear pin devices is that the pin after shearing remains in the bolt and the nut or other tightening member, and may jam them so as to prevent tightening of the nut on the bolt. When this occurs in the hole, there is no way to free the nut.